A significant factor in the efficiency of an internal combustion engine is the degree to which fuel droplets are atomized and vaporized. Ideally, the combustion chamber should contain an air-fuel mixture that is in a completely gaseous state before ignition.
Imparting a vortex to the air-fuel mixture as it enters the combustion chamber improves combustion efficiency. Liquid fuel particles that are swirling in a vortex disburse more readily and evenly than particles that are simply drawn into the combustion chamber without a vortex.
The benefits of imparting a vortex to an air-fuel mixture on its way to a combustion chamber are known. Conventional structure for imparting such a vortex includes valve having helical grooves, valves and valve seat insert having vaned surfaces, and rifled intake ports and manifolds. An example of a valve having helical grooves is disclosed in U.S. Pat. No. 5,771,852 to Heimann, Jr., et al. Examples of conventional valves and valve seat inserts that use vaned surfaces to impart a vortex are found in U.S. Pat. No. 4,744,340 to Kirby for a "vortex generator intake valve," and U.S. Pat. No. 4,389,988 to Ong for a "swirl generating device," which is installed at the opening of a combustion chamber's intake port. U.S. Pat. No. 5,632,145 to Hunt discloses an example of a rifled intake manifold.
Grooves on a valve can impart a vortex to an air-fuel mixture, but a grooved valve presents certain disadvantages. First, a valve is a structural member, and its strength is compromised by removing structural material from its surface to create grooves. Second, only the neck of the valve has enough surface area in contact with the incoming air-fuel mixture to interact significantly with the mixture, and the neck of the valve slows down the air-fuel mixture by the time the mixture approaches it. Consequently, grooves on the neck of the valve cannot interact with the air-fuel mixture as efficiently as grooves in other parts of an engine.
Vaned surfaces present at least two significant problems when placed in the path of an air-fuel mixture in an internal combustion engine. First, vanes used to impart a vortex to the mixture also reduce its intake velocity, which is undesired. Reducing intake velocity of the air-fuel mixture reduces the maximum horsepower of the engine. Second, vanes such as those disclosed in the '988 patent have the potential to break off during operation of the engine. Vane fragments can cause seizure of a piston and destruction of the engine.
Rifling the walls of an intake port or manifold avoids the problems of vaned surfaces. To modify an existing engine to a vortex-inducing configuration, however, a significant portion of the engine must be replaced. For example, an existing engine manifold may be replaced with a rifled manifold such as that disclosed in the '145 patent.
Accordingly, the need remains for an engine component that can be retrofitted into an existing engine in a region where an air-fuel mixture enters the engine's combustion chamber at relatively high velocity. The need further remains for such a component that can be installed as an alternative or in addition to a grooved valve, without the need for replacement of a significant portion of the engine.